/*===-- floatdisf.c - Implement __floatdisf -------------------------------===
 *
 *                     The LLVM Compiler Infrastructure
 *
 * This file is dual licensed under the MIT and the University of Illinois Open
 * Source Licenses. See LICENSE_LLVM.TXT for details.
 *
 *===----------------------------------------------------------------------===
 *
 * This file implements __floatdisf for the compiler_rt library.
 *
 *===----------------------------------------------------------------------===
 */

/* Returns: convert a to a float, rounding toward even.*/

/* Assumption: float is a IEEE 32 bit floating point type
 *             di_int is a 64 bit integral type
 */

/* seee eeee emmm mmmm mmmm mmmm mmmm mmmm */

#include "int_lib.h"

COMPILER_RT_ABI float
__floatdisf(di_int a)
{
    if (a == 0)
        return 0.0F;
    const unsigned N = sizeof(di_int) * CHAR_BIT;
    const di_int s = a >> (N - 1);
    a = (a ^ s) - s;
    int sd = N - __builtin_clzll(a); /* number of significant digits */
    int e = sd - 1; /* exponent */
    if (sd > FLT_MANT_DIG) {
        /*  start:  0000000000000000000001xxxxxxxxxxxxxxxxxxxxxxPQxxxxxxxxxxxxxxxxxx
         *  finish: 000000000000000000000000000000000000001xxxxxxxxxxxxxxxxxxxxxxPQR
         *                                                12345678901234567890123456
         *  1 = msb 1 bit
         *  P = bit FLT_MANT_DIG-1 bits to the right of 1
         *  Q = bit FLT_MANT_DIG bits to the right of 1
         *  R = "or" of all bits to the right of Q
         */
        switch (sd) {
            case FLT_MANT_DIG + 1:
                a <<= 1;
                break;
            case FLT_MANT_DIG + 2:
                break;
            default:
                a = ((du_int)a >> (sd - (FLT_MANT_DIG + 2))) | ((a & ((du_int)(-1) >> ((N + FLT_MANT_DIG + 2) - sd))) != 0);
        };
        /* finish: */
        a |= (a & 4) != 0; /* Or P into R */
        ++a; /* round - this step may add a significant bit */
        a >>= 2; /* dump Q and R */
        /* a is now rounded to FLT_MANT_DIG or FLT_MANT_DIG+1 bits */
        if (a & ((du_int)1 << FLT_MANT_DIG)) {
            a >>= 1;
            ++e;
        }
        /* a is now rounded to FLT_MANT_DIG bits */
    } else {
        a <<= (FLT_MANT_DIG - sd);
        /* a is now rounded to FLT_MANT_DIG bits */
    }
    float_bits fb;
    fb.u = ((su_int)s & 0x80000000) | /* sign */
        ((e + 127) << 23) | /* exponent */
        ((su_int)a & 0x007FFFFF); /* mantissa */
    return fb.f;
}

#if defined(__ARM_EABI__)
AEABI_RTABI float
__aeabi_l2f(di_int a)
{
    return __floatdisf(a);
}
#endif
